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CONVERSION OF GLYCEROL TO GLYCEROL CARBONATE VIA TRANSESTERIFICATION USING 1-ETHYL-3-METHYLIMIDAZOLIUM ACETATE CATALYST

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(1)al. ay. a. CONVERSION OF GLYCEROL TO GLYCEROL CARBONATE VIA TRANSESTERIFICATION USING 1-ETHYL-3-METHYLIMIDAZOLIUM ACETATE CATALYST. of. M. ZATI ISMAH ISHAK. U. ni. ve r. si. ty. THESIS SUBMITTED IN FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY. DEPARTMENT OF CHEMISTRY FACULTY OF SCIENCE UNIVERSITY OF MALAYA KUALA LUMPUR 2018.

(2) UNIVERSITY OF MALAYA. ORIGINAL LITERARY WORK DECLARATION. Name of Candidate: ZATI ISMAH BINTI ISHAK Registration/Matric No: SHC130032 Name of Degree: DOCTOR OF PHILOSOPHY (EXCEPT MATHEMATIC & SCIENCE PHILOSOPHY). a. Title of Project Paper/Research Report/Dissertation/Thesis (“this Work”):. ay. CONVERSION OF GLYCEROL TO GLYCEROL CARBONATE VIA TRANSESTERIFICATION USING 1-ETHYL-3-METHYLIMIDAZOLIUM. al. ACETATE CATALYST. M. Field of Study: MATERIAL CHEMISTRY. I do solemnly and sincerely declare that:. U. ni. ve r. si. ty. of. (1) I am the sole author/writer of this Work; (2) This Work is original; (3) Any use of any work in which copyright exists was done by way of fair dealing and for permitted purposes and any excerpt or extract from, or reference to or reproduction of any copyright work has been disclosed expressly and sufficiently and the title of the Work and its authorship have been acknowledged in this Work; (4) I do not have any actual knowledge nor do I ought reasonably to know that the making of this work constitutes an infringement of any copyright work; (5) I hereby assign all and every rights in the copyright to this Work to the University of Malaya (“UM”), who henceforth shall be owner of the copyright in this Work and that any reproduction or use in any form or by any means whatsoever is prohibited without the written consent of UM having been first had and obtained; (6) I am fully aware that if in the course of making this Work I have infringed any copyright whether intentionally or otherwise, I may be subject to legal action or any other action as may be determined by UM. Candidate’s Signature. Date:. Subscribed and solemnly declared before, Witness’s Signature. Date:. Name: Designation:. ii.

(3) CONVERSION OF GLYCEROL TO GLYCEROL CARBONATE VIA TRANSESTERIFICATION USING 1-ETHYL-3-METHYLIMIDAZOLIUM ACETATE CATALYST. ABSTRACT. In the present research, the synthesis of glycerol carbonate by transesterification of. a. glycerol with diethyl carbonate in a green and efficient process catalyzed by ionic liquid. ay. was comparatively studied. A series of imidazolium and ammonium-based ionic liquids with different anions and conditions optimization (reaction temperature, reaction time,. al. diethyl carbonate/glycerol ratio, solvent and catalyst loading) were screened for the best. M. catalytic activity towards glycerol carbonate synthesis with respect to glycerol conversion and glycerol carbonate yield. It has been revealed that 1-ethyl-3-methylimidazolium. of. acetate ([Emim][Ac]) remarks the highest activity towards glycerol conversion and. ty. glycerol carbonate yield of 93.5%, and 88.7%, respectively at 120 ᵒC, 2.0 hours, molar. si. ratio of diethyl carbonate/glycerol of 2, 0.50 mol% [Emim][Ac] loading with 2.0 wt.% water content. The peak intensities at 1262 cm-1 and 923 cm-1 corresponding to O-H. ve r. bending and 3387 cm-1 corresponding to O-H stretching in glycerol were reduced indicate to glycerol being converted to glycerol carbonate. Meanwhile, the peak at 1750 cm-1. ni. corresponding to C=O and also peaks between 1200 cm-1 to 1000 cm-1 corresponding to. U. C–C and C–O stretching of 2-hydroxyethyl chain showed an increase in intensity. These supported the presence of glycerol carbonate while reaction was in progress. Glycerol carbonate peaks at 61.5 ppm, 67.0 ppm, and 77.5 ppm corresponding to –CH2–O-, –CH2– OH and –CH–, respectively are gradually increased when the reaction solution turned into a single phase at 1.5 hours. Response surface methodology (RSM) showed the interactive effects between selected reaction parameters towards glycerol conversion and glycerol carbonate yield with 92.4% and 91.8%, respectively at optimum reaction. iii.

(4) conditions; reaction temperature of 118 ᵒC, at 1.8 hours with 2.2 of diethyl carbonate/glycerol ratio and 0.42 mol% [Emim][Ac] loading. Recyclability study showed insignificant reduction of glycerol conversion from recovered [Emim][Ac] indicating that [Emim][Ac] could be reused for approximately three times. All the respective peaks of [Emim][Ac] can be comparably resolved with little variation in chemical shift of 1H spectra NMR for each cycle, thus revealing that [Emim][Ac] was successfully recovered. a. with no degradation on its structure. The result of the computational study using a General. ay. Atomic and Molecular Electronic Structure System (GAMESS) software clearly demonstrated that the activation of glycerol proceeds mainly through the hydrogen. al. bonding interaction with [Ac]- anion. On the other hand, diethyl carbonate is also capable. M. of forming hydrogen bonding with imidazolium ring proton at carbon 2 position and hydroxyl group of glycerol. The proposed mechanism of glycerol carbonate synthesis. U. ni. ve r. si. ty. of. agreed well with the theoretical computational study.. iv.

(5) PENUKARAN GLISEROL KEPADA GLISEROL KARBONAT MELALUI TRANSESTERIFIKASI MENGGUNAKAN MANGKIN 1-ETIL-3METILIMIDAZOLIUM ASETAT. ABSTRAK. Dalam kajian ini, sintesis gliserol karbonat melalui tindak balas transesterifikasi gliserol. a. dengan dietil karbonat dalam proses hijau dan cekap dimangkinkan oleh cecair ionik telah. ay. dikaji secara perbandingan dengan terperinci. Cecair ionik berasaskan kation imidazolium dan ammonium yang mempunyai anion yang berbeza serta pengoptimuman. al. parameter-parameter keadaan (suhu tindak balas, masa tindak balas, nisbah molar dietil. M. karbonat/gliserol, pelarut dan muatan pemangkin) telah disaring untuk memperoleh pemangkin yang memberi catatan aktiviti pemangkin yang terbaik terhadap penghasilan. of. gliserol karbonat iaitu berdasarkan peratus penukaran gliserol dan gliserol karbonat. ty. terhasil. Keputusan mendapati, 1-etil-3-metilimidazolium asetat ([Emim][Ac]) memberi. si. catatan aktiviti yang tinggi terhadap tindak balas penukaran gliserol dan gliserol karbonat. ve r. terhasil, iaitu masing-masing sebanyak 93.5% dan 88.7% pada 120 ᵒC, 2.0 jam, nisbah dietil karbonat/gliserol 2, 0.50 mol% muatan [Emim][Ac] dengan 2.0 wt.% kandungan air. Keamatan puncak-puncak iaitu pada 1262 cm-1 dan 923 cm-1 sesuai dengan O-H. ni. lentur dan 3387 cm-1 sesuai dengan O-H teregang pada gliserol berkurang menunjukkan. U. gliserol ditukarkan kepada gliserol karbonat. Dalam pada itu, puncak pada 1750 cm-1 sesuai dengan C=O dan juga puncak antara 1200 cm-1 ke 1000 cm-1 merujuk kepada C-C dan C-O teregang pada 2-hidroksietil menunjukkan peningkatan keamatan. Ini menyokong kehadiran gliserol karbonat apabila tindak balas sedang berlaku. Puncak gliserol karbonat pada 61.5 ppm, 67.0 ppm dan 77.5 ppm bersesuaian dengan –CH2–O-, –CH2–OH dan –CH–, masing-masing secara beransur-ansur meningkat apabila larutan tindak balas berubah menjadi fasa tunggal pada 1.5 jam. Kaedah tindak balas permukaan. v.

(6) (RSM) menunjukkan kesan interaksi antara parameter-parameter tindak balas terhadap tindak balas (penukaran gliserol dan gliserol karbonat terhasil) sebanyak 92.4% dan 91.8% gliserol karbonat terhasil, masing-masing diperolehi dibawah keadaan tindak balas optimum; suhu tindak balas 118 ᵒC selama 1.8 jam dengan 2.2 nisbah dietil karbonat/gliserol dan 0.42 mol% muatan pemangkin [Emim][Ac]. Kajian kitar semula telah menunjukkan pengurangan yang tidak ketara terhadap penukaran gliserol melaui. a. [Emim][Ac] yang dipulih semula dan [Emim][Ac] boleh digunakan semula sehingga. ay. kira-kira tiga kali kitaran. Semua puncak [Emim] [Ac] boleh dilihat dengan hanya sedikit variasi dalam peralihan kimia 1H spektrum NMR untuk setiap kitaran, dengan itu. al. mendedahkan bahawa [Emim][Ac] berjaya dipulihkan tanpa degradasi pada strukturnya.. M. Hasil kajian teori komputer menggunakan perisian General Atomic and Molecular Electronic Structure System (GAMESS) jelas menunjukkan bahawa, gliserol diaktifkan. of. melalui interaksi ikatan hidrogen dengan asetat anion. Sebaliknya, dietil karbonat juga. ty. mampu membentuk ikatan hidrogen dengan proton di kedudukan karbon 2 pada lingkaran. si. imidazolium dan kumpulan hidroksil daripada gliserol. Oleh itu, mekanisma yang. U. ni. ve r. dicadangkan sepadan dengan kajian teori perisian komputer.. vi.

(7) ACKNOWLEDGEMENTS. Firstly, I would like to thank my supervisors, Dr. Nor Asrina Sairi and Prof. Dr. Yatimah Alias, who gave me the opportunity to join UMCIL group and guided me through this research work. By being very supportive, they always made my mind widely open. To my supporting research supervisors Prof. Dr. Mohamed Khaireddine Taieb Aroua and Prof. Madya Dr. Rozita Yusoff, thank you for your guidance. I would like to. ay. a. extend my heartfelt thanks to my labmates1 (UM), colleagues (UPM) and Gelep buddies2 for the bond of friendship and teamwork and also for making my stay in UM a bearable. al. one with many sweet memories and experiences. Without all of you, I would not have. M. made it this far. Special gratitude to my mentor, Sir Mohd Basyaruddin Abd. Rahman for his invaluable guidance and advices. A special thank you also goes to my mom (Gon Binti. of. Daud) and housemate (Yusliza Yusof) for their patience, support and encouragement in. ty. every second. Words cannot express how grateful I am for their care and concern for me. Last but not least, I would also like to express my deepest gratitude for Ministry of. si. Education Malaysia on MYBRAIN 15 scholarship, High Impact Research Grant. ve r. (UM.C/625/1/HIR/MoE/ENG59) and PPP Grant (PG206-2014B) for the research expenses throughout the research period. Without their support, I would have never had. U. ni. the chance to complete this stressful journey with success.. Zati. _____________ 1. Dazylah Darji, Nor Rahimah Said, Wan Melissa Wan Mazlan, Maizathul Akmam, Siti Mastura Mohd Zakaria, Kumuthini. Chandrasekaram, Naimah Haron and labmates. 2. Khairulazhar Jumbri, Emmy Maryati Omar, Asrul Farrish OKR Udaiyappan, Mohd Rizal Chumati, Nur Fariza Abdul Rahman, Siti. Efliza Ashari and Intan Diana Mat Azmi. vii.

(8) TABLE OF CONTENTS. ABSTRACT ................................................................................................................iii ABSTRAK ................................................................................................................... v ACKNOWLEDGEMENTS ...................................................................................... vii TABLE OF CONTENTS .........................................................................................viii LIST OF TABLES .................................................................................................... xii. ay. a. LIST OF FIGURES ................................................................................................. xiv LIST OF SCHEMES ............................................................................................... xxi. al. LIST OF SYMBOLS AND ABBREVIATIONS .................................................xxiii. CHAPTER 1 : INTRODUCTION. M. LIST OF APPENDICES ........................................................................................ xxv. of. 1.1 Background ......................................................................................................... 1. ty. 1.2 Problem statement ............................................................................................... 4. si. 1.3 Objectives of the research ................................................................................... 5. ve r. 1.4 Scope of the research .......................................................................................... 6 1.5 Outline of the thesis ............................................................................................ 8. ni. CHAPTER 2 : LITERATURE REVIEW. U. 2.1 Glycerol ............................................................................................................. 10 2.1.1. Physical and chemical properties of glycerol............................................ 11. 2.2 Glycerol carbonate as a potential value added chemical .................................. 13 2.3 Synthesis routes of glycerol carbonate .............................................................. 14 2.3.1 Direct synthetic route ................................................................................. 18 2.3.1.1 Carboxylation of glycerol with carbon dioxide and carbon monoxide ... 18 2.3.2 Indirect synthetic route ............................................................................... 20. viii.

(9) 2.3.1.1 Phosgene ................................................................................................. 20 2.3.1.2 Urea ......................................................................................................... 21 2.3.1.3 Alkylene carbonate.................................................................................. 22 2.3.1.4 Dialkyl carbonate .................................................................................... 24 2.3.3 Summary on the synthesis routes of glycerol carbonate ............................ 25. a. 2.4 Homogeneous catalyst for transesterification reaction of glycerol with dialkyl. ay. carbonate ................................................................................................................. 26 2.5 Ionic liquids ....................................................................................................... 31. al. 2.5.1 Ionic liquids as catalysts............................................................................. 33. M. 2.5.1.1 Effect of anion to transesterification reaction of glycerol ....................... 37. of. 2.5.1.2 Effect of cation to transesterification reaction of glycerol ...................... 38 2.5.1.3 Synergistic effect of cation and anion to transesterification reaction of. ty. glycerol ................................................................................................................ 39. si. 2.5.1.4 Reported mechanism ............................................................................... 46. ve r. 2.6 Factors influencing transesterification reaction of glycerol .............................. 51 2.6.1 Effect of temperature.................................................................................. 51. U. ni. 2.6.2 Effect of time.............................................................................................. 54 2.6.3 Effect of substrate ratio .............................................................................. 56 2.6.4 Effect of catalyst loading ........................................................................... 58. 2.7 Reusability of ionic liquids ............................................................................... 59 CHAPTER 3 : MATERIAL AND METHOD 3.1 Material and chemicals ..................................................................................... 61 3.1.1 Chemicals for transesterification reaction of glycerol ............................... 61. ix.

(10) 3.1.2 Source of ionic liquids ............................................................................... 61 3.1.3 Solvents ...................................................................................................... 62 3.2 Experimental procedure .................................................................................... 62 3.2.1 Drying of glycerol and ionic liquid ............................................................ 62 3.2.2 Transesterification reaction ........................................................................ 63. a. 3.2.2.1 Screening of ionic liquid as catalyst for transesterification reaction .... 63. ay. 3.2.2.2 General procedure for transesterification reaction ............................... 63 3.2.3 Recycle of ionic liquid ............................................................................... 64. M. al. 3.2.4 Product analysis ......................................................................................... 65 3.2.4.1 Thin layer chromatography (TLC) ....................................................... 65. of. 3.2.4.2 Attenuated total reflection-Fourier transform infrared (ATR-FTIR). ty. spectrometry ..................................................................................................... 65. si. 3.2.4.3 Nuclear magnetic resonance (NMR) spectroscopy .............................. 65. ve r. 3.2.4.4 Gas chromatography-flame ionization detector (GC-FID) .................. 66 3.2.4.5 Gas chromatography-mass spectrometry (GC-MS) ............................. 67. ni. 3.3 Modelling & optimization by response surface methodology (RSM) .............. 68. U. 3.3.1 Experimental design and statistical analysis .............................................. 68. 3.4 Computational Methods .................................................................................... 69. CHAPTER 4 : RESULTS AND DISCUSSION 4.1 Screening of ionic liquid for transesterification reaction .................................. 70 4.1.1 Factors influencing transesterification reaction ......................................... 74 4.1.1.1 Effect of reaction temperature .............................................................. 75 4.1.1.2 Effect of reaction time .......................................................................... 79. x.

(11) 4.1.1.3 Effect of substrate ratio and solvent ..................................................... 81 4.1.1.4 Effect of catalyst loading ...................................................................... 85 4.1.2 Characterization of transesterification reaction of glycerol products ........ 88 4.1.2.1 Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy ..................................................................................................... 88. a. 4.1.2.2 Nuclear magnetic resonance (NMR) spectroscopy .............................. 95. ay. 4.1.2.3 Gas chromatography analysis ............................................................... 98 4.2 Modelling and optimization by Response Surface Methodology (RSM) ....... 107. al. 4.2.1 Design of experiment (DOE) ................................................................... 107. M. 4.2.1.1 Model fitting and analysis of variance (ANOVA) ............................. 107. of. 4.2.2 Interactive effects of variables on conversion .......................................... 115. ty. 4.2.3 Interactive effects of variables on yield ................................................... 121. si. 4.2.4 Optimization of transesterification reaction and model verification........ 127 4.3 Recyclability of ionic liquid catalyst............................................................... 128. ve r. 4.4 Mechanism of transesterification reaction ...................................................... 132. ni. 4.4.1 Computational study ................................................................................ 132. U. 4.4.2 Proposed mechanism................................................................................ 138. CHAPTER 5 : GENERAL CONCLUSION AND FURTHER WORK 5.1 Conclusion ...................................................................................................... 142 5.2 Recommendation for further studies ............................................................... 145 REFERENCES ........................................................................................................ 146 LIST OF PUBLICATION AND PAPER PRESENTED ..................................... 158. xi.

(12) LIST OF TABLES. Table 2.1: Some physicochemical properties and toxicity data of glycerol (Mario & Michele, 2010). ............................................................................................ 11 Table 2.2: Advantages and disadvantages of conversion route with respect to glycerol carbonate yield. ............................................................................................ 15. ay. a. Table 2.3: Comparison of reaction conditions and performance of various catalysts (except of ionic liquid) for glycerol transesterification. ............................... 29. al. Table 2.4: Typical ionic liquids as catalysts use in transesterification reaction. ............ 35. M. Table 2.5: Reaction conditions of ionic liquids as catalyst of glycerol carbonate synthesis. ...................................................................................................................... 41. of. Table 2.6: General comparison between homogeneous classic and ionic liquid catalyst. ...................................................................................................................... 59. ty. Table 4.1: List of ionic liquids used as catalysts in transesterification reaction of glycerol. si. and reported β value (Cláudio et al., 2014). ................................................. 71. ve r. Table 4.2: Catalyst screening of selected ionic liquid as catalyst for transesterification of glycerol. Reaction conditions: Temperature = 120 ᵒC, Reaction time = 2.0. ni. hours, Ratio diethyl carbonate/glycerol = 2 and Catalyst loading = 0.50 mol%. U. based on limiting reactant. ........................................................................... 72. Table 4.3: Effect of water contents in [Emim][Ac] on the glycerol conversion and glycerol carbonate yield. .............................................................................. 85 Table 4.4: FTIR of absorption bands of functional groups of glycerol and possible products formed from transesterification reaction of glycerol and diethyl carbonate. ..................................................................................................... 89. xii.

(13) Table 4.5: Assignment 1H NMR peak of [Emim][Ac]/glycerol mixture. ...................... 98 Table 4.6: Synoptic table of major mass spectroscopy signals of transesterification reaction product. ......................................................................................... 105 Table 4.7: Range of variables for the central composite design (CCD). ...................... 108 Table 4.8: Composition of the various runs of the central composite design (CCD), actual and predicted responses. .................................................................. 111. a. Table 4.9: Analysis of variance (ANOVA) and model coefficients on conversion ..... 112. ay. Table 4.10: Analysis of variance (ANOVA) and model coefficients on yield. ........... 113 Table 4.11:Optimum conditions for transesterification reaction of glycerol and diethyl. al. carbonate generate from response surface model. ..................................... 127. M. Table 4.12: Assignment 1H NMR peak of [Emim][Ac]. .............................................. 131 Table 4.13:Quantum mechanics calculation of reactants and transition states of. of. intermediate and [Emim][Ac] catalyst with hybrid Becke 3-Lee-Yang-Parr. ty. (B3LYP) exchange-correlation functional with the 6-31G basis sets approach for the transesterification reaction of glycerol carbonate synthesis.. U. ni. ve r. si. ……………………………………………………………………….138. xiii.

(14) LIST OF FIGURES. Figure 1.1: Biodiesel production process yielding glycerol as the main by-product. ...... 1 Figure 1.2: Different types of glycerol grades. ................................................................ 2 Figure 1.3: Type of catalyst use for transesterification reaction of glycerol with dialkyl carbonate. ..................................................................................................... 3 Figure 2.1: World outline of current surplus glycerol production (Nanda et al., 2014). 10. ay. a. Figure 2.2: Chemical structure of glycerol..................................................................... 11 Figure 2.3: Value added chemicals from glycerol (Zheng et al., 2008). ........................ 13. al. Figure 2.4: Direct and indirect application of glycerol carbonate (Ochoa-Gómez et al.,. M. 2012a; Pagliaro et al., 2007). ..................................................................... 14 Figure 2.5: Various glycerol carbonate synthesis routes (Ramírez-López, & Belsué,. of. 2012; Sonnati et al., 2013). ........................................................................ 18. ty. Figure 2.6: Comparison between lattice energy of NaCl and [Emim][Cl] (Wilkes, Levisky, Wilson, & Hussey, 1982). ........................................................... 31. si. Figure 2.7: Examples of some typical cations and anions of ionic liquids. ................... 32. ve r. Figure 2.8: DBU based ionic liquid. .............................................................................. 40 Figure 3.1: Drying of ionic liquid by Schenk line.......................................................... 62. U. ni. Figure 4.1: Effect of reaction temperature on the transesterification of glycerol with diethyl carbonate in the presence of [Emim][Ac] as catalyst. Reaction conditions: Reaction time = 2.0 hours, Ratio of diethyl carbonate/glycerol = 2 and [Emim][Ac] loading= 0.50 mol% based on limiting reactant. ......... 76 Figure 4.2: Changes of the colour of reaction solution with respect to the reaction temperature at 2.0 hours, Ratio of diethyl carbonate/glycerol of 2 and 0.50 mol% [Emim][Ac] loading. ....................................................................... 77. xiv.

(15) Figure 4.3: Effect of reaction time on the transesterification of glycerol with diethyl carbonate in the presence of [Emim][Ac] as catalyst. Reaction conditions: Temperature = 120 ⁰C, Ratio of diethyl carbonate/glycerol = 2 and [Emim][Ac] loading = 0.50 mol% based on limiting reactant. ................. 81 Figure 4.4: Effect of diethyl carbonate/glycerol ratio on conversion of glycerol and glycerol carbonate yield and selectivity. Reaction conditions: Temperature. a. = 120 ᵒC, Reaction time = 2.0 hours and [Emim][Ac] loading= 0.50 mol%. ay. based on limiting reactant. ......................................................................... 83 Figure 4.5: Effect of catalyst loading on the transesterification of glycerol with diethyl. al. carbonate in the presence of [Emim][Ac] as catalyst. Reaction conditions:. M. Temperature = 120 ᵒC, Reaction time = 2.0 hours and Ratio of diethyl. of. carbonate/glycerol = 2. .............................................................................. 86 Figure 4.6: Effect of catalyst loading on glycerol carbonate selectivity with respect to. ty. time on transesterification of glycerol with diethyl carbonate. Reaction. si. conditions: Temperature = 120 ᵒC, Ratio of diethyl carbonate/glycerol = 2. ve r. and [Emim][Ac] loading = 0.50 mol% based on limiting reactant. ........... 87 Figure 4.7: ATR-FTIR spectra showing the interactions of glycerol with ionic liquids:. ni. (a) glycerol, (b) glycerol-[Ma][NO3], (c) glycerol-[Ea][NO3], (d) glycerol-. U. [Bmim][Cl], (e) glycerol-[Bmim][BF4], (f) glycerol-[Emim][Dmp], (g) glycerol-[Bmim][Dca],. (h). glycerol-[Hea][Fmt]. and. (i). glycerol-. [Emim][Ac]. The ratio of glycerol to ionic liquid was set at 1. ................. 90. Figure 4.8: Hydrogen-bonding interaction between [Emim][Ac] and glycerol. ............ 91 Figure 4.9: ATR-FTIR spectra of transesterification of glycerol using [Emim][Ac] as catalyst: (a) 30 minutes, (b) 1.0 hour, (c) 1.5 hours, (d) 2.0 hours, (e) 2.5 hours, (f) 3.0 hours, (g) 3.5 hours and (h) 4.0 hours. Reaction conditions:. xv.

(16) Temperature = 120 ᵒC, Ratio of diethyl carbonate/glycerol = 2 and [Emim][Ac] loading= 0.50 mol% based on limiting reactant. .................. 93 Figure 4.10: ATR-FTIR spectra of transesterification of glycerol and diethyl carbonate using [Emim][Ac] as catalyst: (a) glycerol carbonate and glycerol carbonate-[Emim][Ac] of (b), 0.10 mol%, (c) 0.50 mol%, (d) 1.00 mol%, (e) 5.00 mol% and (f) 10.00 mol%. Reaction conditions: Temperature = 120. a. ᵒC, Reaction time = 2.0 hours and Ratio of diethyl carbonate/glycerol. ay. carbonate = 2. ............................................................................................. 94 Figure 4.11: 13C NMR of reaction mixture at selected time interval which is (a) 0 minute,. al. (b) 30 minutes, (c) 1.0 hour, (d) 1.5 hours, (e) 2.0 hours, (f) 2.5 hours and. M. (g) 3.0 hours (zooming at ≈ 60 ppm to 85 ppm for (e), (f) and (g)). Reaction. of. conditions: Temperature = 120 ᵒC, Ratio of diethyl carbonate/glycerol = 2 and [Emim][Ac] loading = 0.50 mol% based on limiting reactant.. ty. Deuterated methanol-d4 (99.8%) was used as solvent in NMR analysis. The ) = glycerol dicarbonate, (●) = glycidol and ( ) =. si. symbol depicted for (. ve r. unknown compounds. ................................................................................ 96 Figure 4.12: 1H NMR spectra for [Emim][Ac] (indicates by blue spectrum) and mixture. (indicates. by. red. spectrum).. ni. [Emim][Ac]/glycerol. U. [Emim][Ac]/glycerol mixture was prepared with ratio of 0.5:5. Deuterated methanol-d4 (99.8%) was used as solvent in NMR analysis. .................... 97. Figure 4.13: Gas chromatography of standard A = glycidol, B = glycerol, C = glycerol dicarbonate and D= glycerol carbonate. A solution of glycerol, glycerol carbonate and glycidol standard was prepared in equivalent ratio. Column FFAP (30 m x 0.25 mm). Injection volume: 1 μl. Oven: 60 ºC held 5 minutes, temperature ramp at 5 ºC/minutes from 60 ºC to 80 ºC, 1 minute. xvi.

(17) hold at 80 ºC, a 10 ºC/minutes ramp from 80 ºC to 230 ºC and a 10 minutes hold at 230 ºC............................................................................................. 99 Figure 4.14: Gas chromatography of glycidol standard (97.0% purity). A = glycidol. Column FFAP (30 m x 0.25 mm). Injection volume: 1 μl. Oven: 60 ºC held 5 minutes, temperature ramp at 5 ºC/minutes from 60 ºC to 80 ºC, 1 minute hold at 80 ºC, a 10 ºC /minutes ramp from 80 ºC to 230 ºC and a 10 minutes. a. hold at 230 ºC........................................................................................... 100. ay. Figure 4.15: Glycidol functionalities. .......................................................................... 100 Figure 4.16: Gas chromatography-flame ionization detector spectra of transesterification. al. reaction of glycerol and diethyl carbonate with respect to the reaction time:. M. (a) 0 minute (b) 1.5 hours (c) 2.0 hours and (d) 3.0 hours. A = glycidol, B = glycerol, C = glycerol dicarbonate and D = glycerol carbonate. Reaction. of. conditions: Temperature = 120 ᵒC, Ratio of diethyl carbonate/glycerol = 2. ty. and [Emim][Ac] loading = 0.50 mol% based on limiting reactant. Column. si. FFAP (30 m x 0.25 mm). Injection volume: 1 μl. Oven: 60 ºC held 5. ve r. minutes, temperature ramp at 5 ºC/minutes from 60 ºC to 80 ºC, 1 minute hold at 80 ºC, a 10 ºC/minutes ramp from 80 ºC to 230 ºC and a 10 minutes hold at 230 ºC........................................................................................... 101. U. ni. Figure 4.17: Possible aliphatic polyglycidol structures form during transesterification of glycerol and diethyl carbonate using [Emim][Ac] catalyst. .................... 103. Figure 4.18: The structure of polyglycidol (a) Growth via an active chain end and (b) via an activated monomer mechanism (Nuyken & Pask, 2013). ................... 104 Figure 4.19: Plots showing correlation of actual and predicted values of conversion (a) and yield (b) by the model and normal probability of residuals conversion (a1) and yield (b1). .................................................................................... 114. xvii.

(18) Figure 4.20: Response surface plot showing the interaction between two parameters, temperature and substrate ratio for transesterification reaction. Other variables are constant at their centre points. The numbers inside the contour plots indicate the conversion (%) of glycerol in transesterification reaction….……………………………………………………………...116 Figure 4.21: Response surface plot showing the interaction between two parameters,. a. temperature and time for transesterification reaction. Other variables are. ay. constant at their centre points. The numbers inside the contour plots indicate the conversion (%) of glycerol in transesterification reaction. ................ 117. al. Figure 4.22: Response surface plot showing the interaction between two parameters,. M. temperature and catalyst loading for transesterification reaction. Other variables are constant at their centre points. The numbers inside the contour. of. plots indicate the conversion (%) of glycerol in transesterification reaction.. ty. ................................................................................................................. 118. si. Figure 4.23: Response surface plot showing the interaction between two parameters, time and catalyst loading for transesterification reaction. Other variables are. ve r. constant at their centre points. The numbers inside the contour plots indicate the conversion (%) of glycerol in transesterification reaction. ................ 119. U. ni. Figure 4.24: Response surface plot showing the interaction between two parameters, time and substrate ratio for transesterification reaction. Other variables are constant at their centre points. The numbers inside the contour plots indicate the conversion (%) of glycerol in transesterification reaction. ................ 120 Figure 4.25: Response surface plot showing the interaction between two parameters, substrate ratio and catalyst loading for transesterification reaction. Other variables are constant at their centre points. The numbers inside the contour. xviii.

(19) plots indicate the conversion (%) of glycerol in transesterification reaction……………………………………………………………….....121 Figure 4.26: Response surface plot showing the interaction between two parameters, temperature and time for transesterification reaction. Other variables are constant at their centre points. The numbers inside the contour plots indicate the yield (%) of glycerol carbonate as product in transesterification. a. reaction..................................................................................................... 122. ay. Figure 4.27: Response surface plot showing the interaction between two parameters, temperature and substrate ratio for transesterification reaction. Other. al. variables are constant at their centre points. The numbers inside the contour. M. plots indicate the yield (%) of glycerol carbonate as product in transesterification reaction. ...................................................................... 123. of. Figure 4.28: Response surface plot showing the interaction between two parameters, time. ty. and substrate ratio for transesterification reaction. Other variables are. si. constant at their centre points. The numbers inside the contour plots indicate the yield (%) of glycerol carbonate as product in transesterification. ve r. reaction..................................................................................................... 124. Figure 4.29: Response surface plot showing the interaction between two parameters,. U. ni. temperature and catalyst loading for transesterification reaction. Other variables are constant at their centre points. The numbers inside the contour plots indicate the yield (%) of glycerol carbonate as product in transesterification reaction. ...................................................................... 125. Figure 4.30: Response surface plot showing the interaction between two parameters, time and catalyst loading for transesterification reaction. Other variables are constant at their centre points. The numbers inside the contour plots indicate. xix.

(20) the yield (%) of glycerol carbonate as product in transesterification reaction..................................................................................................... 126 Figure 4.31: Recyclability study of [Emim][Ac] for transesterification reaction. Reaction conditions: Temperature = 118 ᵒC, Reaction time = 1.8 hours, Ratio of diethyl carbonate/glycerol = 2.2 and [Emim][Ac] loading = 0.42 mol% based on limiting reactant (1st = first recycle, 2nd = second recycle, 3rd = third. a. recycle and 4th = fourth recycle). ............................................................. 129. ay. Figure 4.32: 1H NMR analysis of (a) fresh [Emim][Ac], (b) recovered [Emim][Ac]-2nd recycle and (c) recovered [Emim][Ac]-3rd recycle. Reaction conditions:. al. Heated at 118 ᵒC at 1.8 hours, ratio of diethyl carbonate/glycerol 2.2 and. M. 0.42 mol% [Emim][Ac] loading. Deuterated methanol-d4 (99.8%) was used. of. as solvent in NMR analysis. .................................................................... 131 Figure 4.33: Optimized reactants structure with [Emim][Ac] at initial state of. ty. transesterification reaction using GAMESS software and visualized using. si. Avogadro. Hydrogen bonds are represented by red dash line. ................ 134. ve r. Figure 4.34: Optimized transition state (TS1) structure showing the interaction of [Emim][Ac]. with. ethyl. glyceryl. carbonate. intermediate. during. ni. transesterification reaction using GAMESS software and visualized using Avogadro. Hydrogen bonds are represented by red dash line. ................ 135. U. Figure 4.35: Optimized transition state (TS2) structure showing the interaction of [Emim][Ac]. with. ethyl. glyceryl. carbonate. intermediate. during. transesterification reaction using GAMESS software and visualized using Avogadro. Hydrogen bonds are represented by red dash line. ................ 137. xx.

(21) LIST OF SCHEMES. Scheme 2.1: Synthesis of glycerol carbonate from glycerol and carbon dioxide. .......... 19 Scheme 2.2: Synthesis of glycerol carbonate from glycerol and carbon monoxide. ...... 20 Scheme 2.3: Phosgenation of glycerol carbonate from glycerol and phosgene. ............ 20 Scheme 2.4: Carbonylation of glycerol carbonate with glycerol and urea. .................... 21 Scheme 2.5: Transesterification reaction of glycerol carbonate from glycerol and a). ay. a. ethylene carbonate and b) propylene carbonate. ........................................ 23 Scheme 2.6: Transesterification reaction of glycerol carbonate from glycerol and a). al. dimethyl carbonate and b) diethyl carbonate. ............................................ 25. M. Scheme 2.7: Reaction mechanism of the transesterification of glycerol with dimethyl carbonate using 1-butyl-3-methylimidazolium imidazolide ([Bmim][Im]). of. catalyst. ...................................................................................................... 47. ty. Scheme 2.8: The proposed reaction mechanism for (a) transesterification of dimethyl carbonate with glycerol and (b) decarboxylation of glycerol carbonate. si. catalysed by ionic liquid (Munshi et al., 2014a). ....................................... 48. ve r. Scheme 2.9: Proposed reaction mechanism of transesterification reaction of glycerol and dimethyl carbonate using DABCO-Dimethyl carbonate catalyst (Munshi et. ni. al., 2014c). ................................................................................................. 49. U. Scheme 2.10: Proposed mechanism for glycidol formation (Ochoa-Gómez et al., 2012b). ................................................................................................................... 50. Scheme 2.11: Reaction mechanism of the transesterification of glycerol with dimethyl carbonate.................................................................................................. 50 Scheme 4.1: The proposed mechanism for glycerol carbonate synthesis through catalytic transesterification of glycerol with diethyl carbonate by [Emim][Ac]. ... 139. xxi.

(22) Scheme 4.2: The proposed mechanism for synthesis of possible by-products from glycerol carbonate, a) glycerol dicarbonate and b) glycidol, using. U. ni. ve r. si. ty. of. M. al. ay. a. [Emim][Ac] as catalyst. ......................................................................... 141. xxii.

(23) LIST OF SYMBOLS AND ABBREVIATIONS. - 1-butyl-3-methylimidazolium tetrafluoroborate. [Bmim][Cl]. - 1-butyl-3-methylimidazolium chloride. [Bmim][Dca]. - 1-butyl-3-methylimidazolium dicyanamide. [Bmim][Im]. - 1-butyl-3-methylimidazolium imidazolide. [Ea][NO3]. - ethylammonium nitrate. [Emim][Ac]. - 1-ethyl-3-methylimidazolium acetate. [Emim][DMP]. - 1-ethyl-3-methylimidazolium dimethyl phosphate. [Hea][Fmt]. - 2-hydrozyethylammonium formate. [HOEmim][N(CN)2]. - 1-methyl-3-(2-hydroxylethyl)imidazolium dicyanamide. [Ma][NO3]. - methylammonium nitrate. [Mor1,4][N(CN)2]. - N-methyl-N-butylmorpholinium dicyanamide. [Mor1,g][N(CN)2]. - N-methyl- N-glycerylmorpholinium dicyanamide. ay. al. M. of. ty. ve r. ATR-FTIR. - atmosphere. si. Atm. - Attenuated total reflection-fourier transform infrared - calcium oxide. cP. - centipoise. ni. CaO. U. DMF. a. [Bmim][BF4]. - dimethylformamide. g. - gram. GAMESS. - General atomic and molecular electronic structure system. GC-FID. - Gas chromatography-flame ionization detector. GC-MS. - Gas chromatography-mass spectrometry. K. - kelvin. K2CO3. - potassium carbonate. KOH. - potassium hydroxide xxiii.

(24) - milliliter. mmHg. - millimeter of mercury. mmol. - millimole. MPa. - megapascal. NaOH. - sodium hydroxide. NMR. - Nuclear magnetic resonance. ᵒC. - degree Celsius. ppm. - parts per million. rpm. - rate per minute. TON. - turnover number. UV–VIS. - ultraviolet-visible. μl. - microliter. U. ni. ve r. si. ty. of. M. al. ay. a. ml. xxiv.

(25) LIST OF APPENDICES. APPENDIX A ............................................................................................................... 161 APPENDIX B ............................................................................................................... 163 APPENDIX C ............................................................................................................... 166 APPENDIX D ............................................................................................................... 167. U. ni. ve r. si. ty. of. M. al. ay. a. APPENDIX E ............................................................................................................... 170. xxv.

(26) 1.1 Background. Since biodiesel production has increased rapidly around the world, a fundamental concern in biodiesel industry is the generated biodiesel by-product, glycerol (Figure 1.1).. a. In general, it is estimated that, for 10 tons of biodiesel, 1 ton of glycerol is produced. ay. (10.0% of weight). It is predicted that by 2020 the global production of glycerol will reach. al. 41.9 billion liters (Nanda et al., 2014). The surplus in glycerol decreased its price. U. ni. ve r. si. ty. of. M. significantly which also reduced the profitability margins of biodiesel manufacturers.. Figure 1.1: Biodiesel production process yielding glycerol as the main by-product.. 1.

(27) The crude glycerol is about 80.0% pure and still contained contaminants like soap, methanol, and water. In order to turn this crude glycerol into a usable state for existing or emerging uses, a purification process must take place. During this refinement process residual organic matter, water, salt, methanol, and odors are removed. There are different types of glycerin grades ranging from crude glycerol to refined glycerol (pharmaceutical. Technical Grade Glycerol Purification required. Fit for industrial type applications. Approximately 80% pure. >97% pure. Refined Glycerol Used in cosmetics, pharmaceuticals and food. ay. Crude Glycerol By-product produced during transesterification in the biodiesel production process. a. grade) as shown in Figure 1.2.. M. al. >99.7% Pure. of. Figure 1.2: Different types of glycerol grades.. Utilization of glycerol for the synthesis of value-added chemicals is a theme of. ty. great industrial interest to overcome the surplus of glycerol which inevitably. si. accumulated. As a non-toxic and biodegradable compound, glycerol will provide. ve r. important environmental benefits to the new platform products. Via indirect transesterification reaction, glycerol can be converted to glycerol carbonate and this route. ni. has been proven to be the most promising one. Through this reaction, glycerol is reacted. U. with carbon dioxide derivatives such as dimethyl carbonate and diethyl carbonate (Chiappe & Rajamani, 2012; Rokicki et al., 2005; Ochoa-Gómez et al., 2009) which have favored high glycerol carbonate yield.. Much effort has been devoted to the search for effective catalysts for the transesterification of glycerol. The catalyst can be divided into three types as shown in Figure 1.3 which each can be assigned through a wide spectrum of different catalyst properties categorized either acidic and basic catalysis. Furthermore, understanding of the. 2.

(28) catalyst property and the overall reaction mechanism is both practical and fundamental interest.. Type of catalyst. Acidic catalysis. Basic catalysis. Enzymatic. a. Heterogeneous. ay. Homogeneous. M. al. Figure 1.3: Type of catalyst use for transesterification reaction of glycerol with dialkyl carbonate.. The emergence of the green solvent such as ionic liquid with unique properties has. of. gradually gained its versatile application as solvent and catalyst in the process synthesis. ty. (Mohammad Fauzi & Amin, 2012). The adjustable cation-anion pairing opens up the possibility of preparation of acidic or basic ionic liquids (Gong et al., 2008). Dual function. si. of ionic liquids (catalyst and solvent) often leads to an increase in rate and/or reactivity. ve r. compared to some of the catalysts that need the addition of solvent to enhance the reaction (Takagaki et al., 2010; Kumar et al., 2012). Thus, a huge interest on investigating the. ni. usefulness and the scope of ionic liquids as the catalyst in organic reactions and catalysis. U. has been sufficiently reviewed (Wasserscheid & Welton, 2003; Olivier-Bourbigou et al., 2010), and still a lot of reported studies are expecting to come in foreseeable future.. 3.

(29) 1.2 Problem statement. The increasing demand of biodiesel makes glycerol as a by-product available in large quantities at decreasing prices. This has prompted the conversion of low-cost glycerol to value-added products (Teng et al., 2014; Sonnati et al., 2013; Ochoa-Gómez et al., 2012b). One of them is multifunctional glycerol carbonate which has increasing industrial attention based on its physical properties as well as on its reactivity.. ay. a. Transesterification of glycerol with dialkyl carbonate is one of the most direct and industrial feasible pathway to produce high glycerol carbonate yield. Catalyst plays a. al. crucial role in the transesterification reaction of glycerol to glycerol carbonate. It is. M. imperative to search for suitable catalysts that can attainably synthesize glycerol carbonate with regards to reducing the cost of operation and handling, bio-based, reusable. of. through several cycles of reaction and involving chemical (catalytic) processes with. ty. reduced impacts on health, safety, environment, and energy.. si. Various heterogeneous catalysts have been reported for glycerol carbonate. ve r. synthesis from glycerol and dimethyl carbonate. Many of them show a good catalytic activity for glycerol carbonate formation (Lu et al., 2013; Jiabo & Wang, 2011; Climent. ni. et al., 2010; Malyaadri et al., 2011). These catalysts are usually alkali metal oxide or. U. mixed oxide catalysts. However, the preparation method of these catalysts usually is not environmentally friendly and it is time-consuming. Moreover, the catalyst such as calcium oxide (CaO) is deactivate more easily, evidenced by quick decrease of glycerol conversion during the catalyst recycling experiments (Ochoa-Gómez et al., 2009; Jiabo & Wang, 2011) which implies that, an expensive and troublesomely regeneration step following every reaction will be needed for CaO catalyst. Consequently, the cost associated with the preparation could affect the applicability of these catalysts in the industrial scale. 4.

(30) During the period from 2011 to 2016, more than 10,000 publications reported the great impacts of ionic liquids that can be designed to catalyze variety of reactions with excellent catalytic activity influencing the outcome of organic synthesis. It can be seen that less than 2000 publications have reported on ionic liquids as the catalysts in transesterification reactions of glycerol to glycerol carbonate (statistic from google scholar). Regardless of the reported excitements for transesterification reaction of. a. glycerol using various homogeneous as well as heterogeneous catalysts, the limitations. ay. such as high catalyst loading (up to 10.00 mol%) and a large excess of substrate ratio between carbonylating source (dimethyl carbonate and diethyl carbonate) and glycerol. al. (normally 3 to 10) need to be employed in order to achieve good glycerol conversions. M. and high glycerol carbonate yield and selectivity in a reasonable time frame. Moreover, the factors governing the selectivity pattern such as the formation of glycerol carbonate. of. or other possibility products are not well understood. Almost all the literature does. ty. investigate the pertinent factors influencing glycerol conversion and glycerol carbonate. si. yield and/or selectivity, and just few studies focused on the detailed understanding of the fundamental underlying the reaction. These knowledge gaps constituted the starting point. ve r. for experiments in this study.. U. ni. 1.3 Objectives of the research. The aim of this research is to investigate potential ionic liquids as catalyst for. transesterification reaction of glycerol with diethyl carbonate and demonstrates the effect of reaction temperature, time, substrate molar ratio, catalyst loading, water content and basicity of catalyst towards glycerol conversion and glycerol carbonate yield and selectivity. Specific objectives of this research are as follows:. 5.

(31) 1) To explore potential ionic liquids as catalysts and evaluate the affecting parameters for transesterification of glycerol to glycerol carbonate. 2) To study the interactive effects between reaction parameters using Response Surface Methodology (RSM) approach. 3) To explore on recyclability of ionic liquid at optimum usage for transesterification of glycerol.. a. 4) To elucidate the transesterification reaction mechanism theoretically using a. ay. computational method.. M. al. 1.4 Scope of the research. In view of the recent interest in converting glycerol to glycerol carbonate, ionic. of. liquid was used as catalyst for the transesterification reaction of glycerol and diethyl carbonate. Thus, the scope of the current research is divided into four main sections. For. ty. the first part, the performance of ionic liquid as catalyst towards transesterification of. si. glycerol was measured by screening the potential ionic liquids. The approach was to use. ve r. ionic liquid with targeted anion in order to obtain a satisfying glycerol conversion and glycerol carbonate yield and selectivity. Selection of ionic liquids was governed by the. ni. basicity value (β value) originated from the anion of the ionic liquids. Pertinent factors. U. affecting the glycerol conversion and glycerol carbonate yield and selectivity such as the effect of temperature, reaction time, substrate ratio diethyl carbonate/glycerol, solvent, catalyst loading and water content of catalyst were evaluated individually. It was necessary to use Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) in order to corroborate the results obtained from product analysis using gas chromatography-flame ionization detector (GC-FID). Gas chromatography-mass spectrometry (GC-MS) was used to distinguish glycerol carbonate as the main product and also possible unknown products which have been formed along the reaction. 6.

(32) In the second part, statistical method, namely response surface methodology (RSM) was employed to determine the interactive effects between reaction parameters (factors that affect transesterification reaction of glycerol) that yielded the desired responses which are glycerol conversion and glycerol carbonate yield for a given measurement and described the responses near to optimum.. a. In the third part, the investigation on the possibility of recycling the ionic liquid. ay. employed for the consequence cycle of transesterification reaction was performed. The efficiency of recovery was examined along with the glycerol conversion and glycerol. M. al. carbonate yield and selectivity.. In order to support the experimental findings, a computational study was also. of. carried out in the last part. The mechanistic study was conducted by general atomic and. ty. molecular electronic structure system (GAMESS) software. In this study, the fundamental. si. understanding of the role of anion and cation towards the transesterification reaction of glycerol and diethyl carbonate was achieved by prediction of the hydrogen bonding. ve r. formed, thus help to stabilize the reaction during the reactants at initial state and transition states. The reaction mechanism was also proposed by means of the computational. U. ni. findings.. Therefore, it is important to gather overall understanding in the catalytic. transesterification reaction of glycerol and diethyl carbonate using ionic liquid as catalyst as well as optimizing the catalytic reaction. The novelty of this study relies on the fundamental and practical levels as to gather overall understanding in the catalytic transesterification reaction of glycerol and diethyl carbonate using ionic liquid as catalyst. It is envisaged that this study could contribute towards creating a variety of new strategies. 7.

(33) for converting glycerol as a green building block glycerol together with ionic liquids for the more integrated process.. 1.5 Outline of the thesis. In order to accomplish the objectives, this thesis is divided into five chapters. ay. a. which consist of the following chapters:. Chapter 1 describes the research background, problem statements, objectives,. M. al. scope of work and the layout of the thesis.. Chapter 2 consists of relevant literature that motivates this study. It starts with a. of. brief introduction of the background of the source of surplus glycerol and its properties. A broad literature review on the glycerol as a major chemical platform, glycerol carbonate. ty. and organic synthetic routes of converting glycerol to glycerol carbonate were presented. si. in this chapter. Furthermore, it also reviews the properties of ionic liquids as catalysts,. ve r. factors affecting transesterification reaction and reaction mechanism.. ni. Chapter 3 provides the details of the materials, experimental and analytical. U. apparatus including TLC, ATR-FTIR, NMR, GC-FID and GC-MS as well as methodology involved in the experiments.. Chapter 4 describes the results obtained from the transesterification of glycerol and diethyl carbonate by a screening of ionic liquids and reaction parameters such as temperature, time, substrate molar ratio and solvent, catalyst loading and water content. Glycerol conversion and glycerol carbonate yield and selectivity were measured by using GC-FID, while the results from ATR-FTIR, NMR and GC-MS were included to 8.

(34) corroborate the GC-FID’s results. The RSM was reported with the purpose of establishing the relationship between the reaction variables (reaction temperature, time, substrates ratio and catalyst loading) and the responses (glycerol conversion and glycerol carbonate yield) and determine how the responses are affected by the changes in the factors over a specified level of interest. Recyclability of ionic liquid catalyst was also reported for optimum glycerol conversion and glycerol carbonate yield and selectivity. Finally, this. a. chapter also involves the results and the discussion on the computational study, which. ay. have been conducted by GAMESS and the discussion of the proposed mechanism.. al. Chapter 5 emphasizes and summarizes all the significant findings from this. U. ni. ve r. si. ty. of. essential and related to this work.. M. research. Furthermore, relevant suggestions for future work were also provided, which is. 9.

(35) 2.1 Glycerol. Today, as a result of the remarkable growth of biodiesel production produced from vegetable oils by transesterification processes with methanol or ethanol, the production. a. of unavoidable glycerol increased very rapidly as well. The world outline of glycerol. ay. production is given in Figure 2.1. It is predicted that by 2020 the global production of. al. glycerol will reach 41.9 billion liters (Nanda et al., 2014). Thus, crude glycerol disposal and utilization have become a serious issue and a financial and environmental liability for. M. the biodiesel industry should be seriously reconsidered. A large amount of glycerol. of. generated may become an environmental problem since it cannot be disposed in the environment. Economic utilizations of glycerol for value-added products are critically. ty. important for the sustainability of the biodiesel industry. Therefore, new methods for. ve r. si. converting glycerol into high value-added chemicals are being developed.. 35. 36.0. 30. U. ni. Production (billion liters). 40. 30.8. 25. 25.9. 20 15. 17.2. 10 5. 7.8. 0 2006. 2009. 2012. 2015. 2018. Year. Figure 2.1: World outline of current surplus glycerol production (Nanda et al., 2014).. 10.

(36) 2.1.1. Physical and chemical properties of glycerol. Glycerol (glycerine or 1,2,3- propanetriol) is an organic compound and it has the chemical formula C3H8O3 (Figure 2.2). Glycerol is virtually non-toxic to both human and environment. In pure form, glycerol is a clear, colorless, odorless, hygroscopic, vicious and sweet-taste liquid, which possesses a unique combination of physical and chemical. a. properties. Table 2.1 shows physicochemical properties and toxicity data of glycerol.. ay. OH. M. al. OH. Some physicochemical properties and toxicity data of glycerol (Mario & Michele, 2010).. of. Table 2.1:. HO. Figure 2.2: Chemical structure of glycerol.. Toxicity data 17.8 ᵒC 290 ᵒC 92.09 g/mol 1200 cP < 1mm Hg. Density (20 ᵒC) Flash point Autoignition temperature Critical temperature Critical pressure. 1.26 g cm-3 160 ᵒC (closed cup) 400 ᵒC 492.2 ᵒC 42.5 atm. U. ni. ve r. si. ty. Properties Melting point Boiling point Molecular weight Viscosity (20 ᵒC) Vapour pressure (20 ᵒC). Because it is a trihydric alcohol, glycerol is a polar protic solvent with a dielectric. constant of 42.5 (at 25 ᵒC) which is intermediate between that of water (78.5) and an ionic liquid such as 1-butyl-3-methylimidazolium hexafluorophosphate (11.4). The threehydroxyl groups in glycerol dominate its solubility. Glycerol is completely soluble in water and short chain alcohols, sparingly soluble in many common organic solvents (ethyl acetate, dichloromethane, diethyl ether), and is insoluble in hydrocarbons (Mario. 11.

(37) & Michele, 2010). Other than that, the extensive intermolecular hydrogen bonding is responsible for the high viscosity and boiling point of glycerol. Taking advantage of its high boiling point, reactions in glycerol can be carried out at high temperatures, thus allowing acceleration of the reaction.. Glycerol represents an important raw compound in numerous fine chemistry (e.g.. a. food, drug, cosmetic and tobacco industry) and bulk industrial chemical processes due to. ay. its high chemical reactivity (Pagliaro et al., 2007). A highly functionalized nature exhibited by glycerol is due to the presence of primary and secondary hydroxyl groups. al. that can be replaced with other chemical groups. The primary hydroxyl groups generally. M. are more reactive than the secondary hydroxyl group, thus will preferably react first. In any reaction, however, the second and third hydroxyls will react to some extent before all. of. the most reactive groups are exhausted. A large number of top-value added chemicals. ty. such as dihydroxyacetone, mesoxalic acid, 1,3-propane-diol, 1,3-dichloropropanol,. si. glyceryl ethers, glycerol carbonate, and glyceryl esters can be obtained from glycerol by a variety of chemical reactions (Figure 2.3) (Zheng et al., 2008). There is a comprehensive. ve r. literature and various research works are available on the glycerol valorization to valueadded chemicals (Pagliaro et al., 2007; Pagliaro et al., 2009; Behr et al., 2008). Among. ni. them, the production of glycerol carbonate plays a prominent role as the monomer which. U. could be used for the production of new functionalized polymers that might have an interesting new application (Ochoa-Gómez et al., 2012a).. 12.

(38) OH OH. HO O. O Glyceric acid. OH. Dihydroxyacetone Oxidation. H. Reduction. OH. Reduction. OH. HO. O. O O Oxaic acid. O Hydroxypyruvic acid Dehydration. Chloridation. Transesterification. HO. OH. Glycerol O. OH. O. Etherification Etherification. H. OH. Oxidation O Acrolein OH. O Acrylic acid. ay. O. O. Mesoxalic acid. HO. Oxidation. OH 1,2-Propanediol. OH O. O O Tartronic acid. O Glyceraldehyde. HO. OH. OH. HO. OH HO 1,3-Propanediol. HO. HO. a. HO. O. OH. Cl. Cl. Dichloropropanol. al. OH Glycerol carbonate. Cl O Epichlorohydrin. OH. OR1. OR1. Monoglyceride. mono-, di- and tri-tert-butyl ethers as oxygenate fuels. O. OH. n Polyglycerols. of. Diacylglycerol. HO. M. R2O. HO. OH. OH. ty. Figure 2.3: Value added chemicals from glycerol (Zheng et al., 2008).. ve r. si. 2.2 Glycerol carbonate as a potential value-added chemical. With a focus on recent developments in the conversion of glycerol into value-. ni. added chemicals, production of glycerol carbonate is one of the glycerol derivatives that captures at present more scientific and industrial attention. The interest of glycerol. U. carbonate as a bio-based product has broad spectrum of applications in several fields, mainly as a green solvent in analytical applications (Lameiras et al., 2011), Li-ion batteries (Ochoa-Gómez et al., 2012a) or as reaction media (Benoit et al., 2010; Ou et al., 2011). Glycerol carbonate could also serve as raw material for the production of glycidol (Yoo et al., 2001), which is widely being used in the textile, plastics, pharmaceutical and cosmetics industries. Due to its potential end uses, glycerol carbonate is a relatively new product for chemical industry for two main reasons: (1) its wide reactivity, implying. 13.

(39) numerous applications, (2) as a way to valorize glycerol, which is becoming widely available as a major bio-based by-product from the manufacturing of biodiesel and other. M. al. ay. a. chemicals (Behr et al., 2008) (Figure 2.4).. si. ty. of. Figure 2.4: Direct and indirect application of glycerol carbonate (Ochoa-Gómez et al., 2012a; Pagliaro et al., 2007).. ve r. 2.3 Synthesis routes of glycerol carbonate. Figure 2.5 enumerates six proposed synthesis routes of glycerol carbonate. These. ni. include direct carbonylation of glycerol with carbon dioxide and oxidative carbonylation. U. of glycerol with the gaseous mixture of carbon monoxide. For indirect carbonylation, the routes include phosgenation, glycerolysis of urea and transesterification of alkyl carbonates and dialkyl carbonates. Their advantages and limitations are presented in Table 2.2 to exhibit the influence of catalyst on glycerol carbonate synthesis process.. 14.

(40) Advantages. Disadvantages. Glycerol + Carbon dioxide. Sn, KOH/HCl, La2O2CO3–ZnO, nBu2Sn(OMe)2, nBu2SnO, RhCl3 + PPh3 + KI. Using bio-based reactant and commercially available at low price, no intermediate steps. Glycerol + Carbon monoxide. CuCl, CuBr2, PdCl2(1,10phenanthroline) /KI (include addition of oxygen). Straightforward synthetic method. al ay. Catalyst. Higher reaction temperature and pressure and longer heating time, poor carbon dioxide reactivity, thermodynamically limited, use of organic solvents to enhance the reaction rate and improve yield (from 7.0% to 35.0%), difficult recovery of products, formation of polyglycerols at higher temperature. Glycerol carbonate Reference yield (%) 7.0-90.0 Ma et al., 2012; (Free of Ochoa-Gómez solvent), et al., 2011 0.2-35.0 (Organic solvent). U. ni. ve. rs i. ty. of. Direct route. Type. M. Route. a. Table 2.2: Advantages and disadvantages of conversion route with respect to glycerol carbonate yield.. Formation of large amount of byproducts, toxicity of carbon monoxide, difficult in handling, higher reaction pressure. 47.0 (Free of solvent), 83.0-96.0 (Organic solvent). Hu et al., 2010; Mizuno et al., 1994; Wang et al., 2013. 15.

(41) U. ni. al ay. Nemirowsky, 1885. M. Easy separable and Need low pressure, formation of 28.0-93.0 recyclable of ammonia as by-product, difficult heterogeneous purification catalyst. Low cost raw material with low toxicity. of. Glycerol + Alkylene carbonate (Ethylene carbonate/ Propylene carbonate) Glycerol + Dimethyl carbonate. Zn/Ca/ Ma/ Zr/Al2/La2 oxide, ZnSO4, MnSO4, Zn hydrotalcite, γzirconium phosphate, gold, gallium, and zinc supported on oxides and Zeolite ZSM-5 Amberlyst A26 HCO3, zeolite, Al/MgO hydrotalcite, Al/Mg, MgO, RNXMCM41, Amberlyst A26 OHAmmonium bromide, K2CO3, K2CO3/MgO, Sn, CaO,Ca(OH)2, LiNO3/Mg4AlO5.5,M g-Al hydrotalcite, Mg/Al/Zr, hydrotalcitehydromagnesite, lipase. -. Easy separable and Carbonylation agent expensive, 68.0-92.0 recyclable of difficult purification (Free of heterogeneous catalyst solvent). Cho et al., 2010; Vieville et al., 1998. rs i. Glycerol + Urea. Simple and effective Toxic gas, corrosive way of reaction. ty. Glycerol + Phosgene. ve. Indirect route. a. Continue…. Homogeneous catalyst enhanced reaction rate, non-corrosive, higher product obtained, for enzyme (ambient reactions condition, simplicity in purification of products). Product yield decrease and polymerization of product at higher temperature, involve consecutive steps of catalyst preparation, costly. 59.0-99.0 (Free of solvent), 79.0-99.0 (Organic solvent). Kumar et al., 2012; Waghmare et al., 2015; Teles et al., 1994; Tudorache et al., 2014; Liu et al., 2014. 16.

(42) a. Higher product obtained, nonpolluting. Expensive and denaturation (for enzyme). al ay. 1,3dicholorodistannoxa nes, Mg/Al hydrotalcite supported on Al2O3, lipase. U. ni. ve. rs i. ty. of. M. Continue… Glycerol + Diethyl carbonate. 95.0-99.0 (Free of solvent), 84.0 (Organic solvent). Álvarez et al., 2010; Álvarez et al., 2012; Wang & Cao, 2011. 17.

(43) Synthesis route of glycerol carbonate. Direct. Indirect. Glycerol + Carbon dioxide. Glycerolysis. Glycerol + Phosgene. Transesterification. Glycerol + Alkylene carbonate. a. Phosgenation. Glycerol + Urea. ay. Carboxylation. Glycerol + Dialkyl carbonate. M. al. Glycerol + Carbon monoxide and oxygen. ty. 2.3.1 Direct synthetic route. of. Figure 2.5: Various glycerol carbonate synthesis routes (Ramírez-López, & Belsué, 2012; Sonnati et al., 2013).. si. 2.3.1.1 Carboxylation of glycerol with carbon dioxide and carbon monoxide. ve r. Direct carboxylation of glycerol by carbon dioxide could be considered as the. most attractive and environmentally benign pathway leading to glycerol carbonate. ni. production because the process uses carbon dioxide, a global warming gas, as a raw. U. material, and the only by-product is water (Scheme 2.1). Accordingly, a number of homogeneous and heterogeneous catalysts such as zeolites (under supercritical conditions), CeO2/Al2O3, Sn-based compounds and rhodium complexes modified with phosphine ligands have been developed for the carboxylation of glycerol (Aresta et al., 2006; Dibenedetto et al., 2011; Ezhova et al., 2012; George et al., 2009; Vieville et al., 1998). However, the result has never been satisfactory in terms of glycerol carbonate yield and selectivity. Up to now, the poor carbon dioxide reactivity has led to yields lower. 18.

(44) than 8.0%, although a more promising yield of 32.0% has been reported by George et al. (2009). The low catalytic activities of catalyst were also reported even under high pressure because of the thermodynamic limitation (Aresta et al., 2006; Dibenedetto et al.,. al. ay. a. 2011; Vieville et al., 1998).. of. M. Scheme 2.1: Synthesis of glycerol carbonate from glycerol and carbon dioxide.. Aresta et al. (2006) has reported the direct carboxylation of glycerol with carbon. ty. dioxide using tin complexes (n-Bu2Sn(OCH3)2, n-Bu2SnO and Sn(OMe)2) as catalysts.. si. The high temperature of 180 °С and a pressure of 50 atm were employed in the reaction.. ve r. The conversion of glycerol was only 2.3% at 6.0 hours, 5.0 MPa and 453 K. In an attempt to increase the glycerol carbonate yield, molecular sieves were used to remove water from. ni. the gas phase and tetraethylene glycol dimethyl ether was used as a solvent. These have. U. led to a slight increase of glycerol carbonate yield up to 35.0% at 4.0 hours, 13.8 MPa and 393 K. At higher pressure, carbon dioxide occurs in the liquid state thus required special expensive equipment to handle. Other than that, coupling agents (Tomishige et al., 2004), co-reactant such as ethylene carbonate (Vieville et al., 1998), solvents such as ethanol, n-butyl alcohol, acetone, tetrahydrofuran, pyridine, dimethyl sulfonate and dimethylformamide and dehydrating agent such as valeronitrile, benzonitrile, phenyl acetonitrile, 2-cyanopyridine (Liu et al., 2016) were also added to increase glycerol carbonate yield.. 19.

(45) Carboxylation of glycerol with carbon monoxide and oxygen has also been previously reported (Scheme 2.2). Although it is a straightforward reaction, but this method has few drawbacks such as rigorous reaction conditions, formation of large number of by-products, toxicity of carbon monoxide and inherent difficulty to handle it safely both at laboratory and industrial scales (Hu et al., 2010; Mizuno et al., 2010; Teles. al. ay. a. et al., 1994; Wang et al., 2013).. of. M. Scheme 2.2: Synthesis of glycerol carbonate from glycerol and carbon monoxide.. ve r. si. 2.3.1.1 Phosgene. ty. 2.3.2 Indirect synthetic route. The indirect synthetic route involved phosgenation using phosgene shows to be a. ni. very simple and effective way to produce organic carbonates. Phosgenation reaction is. U. somehow hazardous due to the toxicity of phosgene, thus the use of phosgene is limited (Climent et al., 2010; Sonnati et al., 2013) (Scheme 2.3).. Scheme 2.3: Phosgenation of glycerol carbonate from glycerol and phosgene.. 20.

(46) 2.3.1.2 Urea. As an alternative to carbon dioxide, urea has been extensively investigated as in indirect synthetic route (Scheme 2.4). This is a phosgene-free process that uses easily available and low-cost raw materials with low toxicity. Carbonylation of glycerol with urea are catalyzed by basic oxides; magnesium oxide (MgO) and calcium oxide (CaO),. a. Al/Mg and Al/Li mixed oxides (Climent et al., 2010), samarium exchanged heteropoly. ay. acid (Ramesh Kumar & Jagadeeswaraiah, 2012), zirconium phosphate (Aresta et al., 2009), zinc compounds, lanthanum-based mixed oxide (Zhang & He, 2014), gold and. al. palladium based supported (Ab Rahim et al., 2013), hydrotalcite based (Aresta et al.,. M. 2009; Climent et al., 2010; Park et al., 2012), boiler ash (Indran et al., 2014) and tin-. ve r. si. ty. of. tungsten mixed oxide (Jagadeeswaraiah et al., 2014).. U. ni. Scheme 2.4: Carbonylation of glycerol carbonate with glycerol and urea.. Mouloungui et al. (1996) patented the synthesis of glycerol carbonate by. carbonylation of glycerol with urea in the presence of a catalyst bearing Lewis acid sites, in particular, metallic or organometallic salts or supported metallic compounds. Okutsu & Kitsuki (2001) have prepared glycerol carbonate by reacting glycerol with urea with zinc oxide (ZnO) in the presence of a dehydrating agent such as anhydrous magnesium sulfate (MgSO4). After 6.0 hours of reaction time, the conversion of glycerol was 62.0% to 65.0% with a selectivity close to 92.0%. Catalysts based on zinc, Zn(CH3C6H4-SO3)2,. 21.

(47) were used by Yoo & Mouloungui (2003) to synthesize glycerol carbonate from glycerol with urea and glycerol conversion achieved was 85.0% after 1.0 hour of reaction. A recent study by Nguyen-Phu et al. (2016) showed that Zn/Al mixed oxide was successfully impregnated into activated red mud which attained a glycerol carbonate yield of 59.8%, which is higher than 49.6% of the unsupported catalyst, Zn7Al3Ox.. a. Although the urea process is highly efficient for the production of glycerol. ay. carbonate, the reaction must be conducted at elevated temperature (Turney et al., 2013). al. and consumes a relatively longer reaction time about 1.0 hours to 8.0 hours (Sharath Babu et al., 2015). Moreover, the reaction is preferably carried out under vacuum, in particular. M. at a pressure of between 10.03 Pa and 2.14 Pa, so as to displace the point of equilibrium. ty. of. of the reactions by continuously eliminating ammonia from the gaseous state.. ve r. si. 2.3.1.3 Alkylene carbonate. Transesterifications are highly useful reactions for utilization of recent huge. ni. amount of glycerol production originated biodiesel synthesis from triglyceride and methanol (Andreani & Rocha, 2012). Transesterification of glycerol with alkylene. U. carbonate (ethylene carbonate/propylene carbonate) is a safer and more effective method that involves much lower reaction temperature and high yield of glycerol carbonate (Alvarez et al., 2010; Climent et al., 2010; Mouloungui et al., 1996). Ethylene carbonate possesses interesting physical properties such as low toxicity, low evaporation rate, biodegradability and high solvency.. 22.

(48) At present, potassium hydroxide (NaOH) (Esteban et al., 2016), Mg/Al hydrotalcite (Climent et al., 2010), Zn/Al hydrotalcite (Climent et al., 2010), potassium carbonate and MCM-41 based materials (Cho et al., 2010) have been used to catalyze the transesterification reaction of glycerol and ethylene carbonate. Moreover, the transesterification of glycerol in supercritical carbon dioxide using zeolites or strongly basic resins gives low glycerol carbonate yields (less than 25.0%) (Vieville et al., 1998).. a. Through this route (Scheme 2.5 (a)), ethylene glycol was formed as a by-product with a. ay. high boiling point. Reducing the pressure is necessary during purification step to separate. al. ethylene glycol from the glycerol carbonate production process.. O. OH HO. ethylene carbonate. O O. O. HO. OH. 35 °C, 0.5 wt.% OH glycerol carbonate. si. Yield = 87%. ethylene glycol. U. ni. ve r. b). O. ty. glycerol. O. Al/Ca-mixed oxide. of. OH. M. a). Scheme 2.5: Transesterification reaction of glycerol carbonate from glycerol and a) ethylene carbonate and b) propylene carbonate.. Despite promising metal-containing catalyst systems that have been developed for the synthesis of glycerol carbonate from glycerol and ethylene carbonate, ethylene carbonate is expensive. Thus, it is an urgent to find an efficient, inexpensive, and also environmental-friendly metal-free catalytic system for this interesting reaction. 23.

Rujukan

DOKUMEN BERKAITAN

The main parameters that affect the biodiesel yield during transesterification and esterification process are catalyst loading, methanol to oil molar ratio, reaction

Figure 4.23 shows the surface response plot for the effect of catalyst loading, methanol to oil molar ratio on the FAME yield at constant reaction temperature of 80 ˚C and 4.5

(iii) To analyse the relationship between the reaction time, temperature, catalyst loading, and oil-to-methanol molar ratio on biodiesel production using RSM.. 1.6

In Figure 9, through a 2D contour graph, it shows the relationship between time at 4 hours and the glycerol mass in the range 60 - 90 g resulting in a higher GML yield response..

All reaction parameters (temperature, time, catalyst loading, and glycerol to acetic acid molar ratio) have been optimized to obtain the highest selectivity to

Therefore, in the pres- ent study glycerol hydrogenolysis will carried out over Ru/bentonite using at different solid acid catalyst (zeolite, ZrO 2 , Nb 2 O 5 and amberlyst)

The effect of reaction time was studied using 9:1 methanol to oil ratio for cockle shell catalyst and 3:1 ratio for commercial CaO catalyst at 60°C reaction

Figure 4.16 Three-dimensional response surface plot of biodiesel yield for CPO (effect of amount of catalyst and reaction time, methanol to oil molar ratio = 12, temperature =..